Hughes S H, Petropoulos C J, Federspiel M J, Sutrave P, Forry-Schaudies S, Bradac J A
BRI-Basic Research Program, NCI-Frederick Cancer Research Facility, Maryland 21701.
J Reprod Fertil Suppl. 1990;41:39-49.
Strain improvement of agriculturally important animals will require efficient techniques for gene delivery, the ability to regulate the expression of the newly introduced genes and, most important, the identification of genes whose appropriate expression could cause improvement of the animal. We have developed a series of avian retroviral vectors that can be used to introduce new genetic information into the germ line of chickens, for which transgenics cannot be created by direct microinjection of DNA into fertilized eggs. We have identified a 220-bp segment of the chicken skeletal muscle alpha-actin gene that can cause other genes to be expressed specifically in striated muscle. This chicken promoter shows correct tissue specificity in transgenic mice and presumably could be used in other mammalian species. The skeletal muscle alpha-actin promoter has been inserted into the avian retroviral vectors and the promoter is functional in cultured cells infected by these retroviral vectors. The tissue specificity of the expression of the skeletal muscle alpha-actin promoter carried by the retroviral vectors will soon be tested in vivo. We are studying two types of genes that might be useful in strain improvement; genes that could produce dominant resistance to infection by pathogenic viruses, and genes that could play critical roles in muscle development. Expression of the envelope glycoprotein of retroviruses can specifically block the cellular receptor that viruses use to infect a susceptible cell. Expression of the avian leukosis virus subgroup A envelope in transgenic chickens prevents infection by pathogenic viruses of the same subgroup. We are attempting to block reticuloendotheliosis virus infection by expressing the reticuloendotheliosis envelope glycoprotein. We have shown that we can block infection in cultured cells, and we are now creating retroviral vectors for experiments in vivo. We have also begun to study the cellular homologue of the ski oncogene, which has been shown to stimulate the differentiation of quail myoblasts in vitro. Biologically active cDNAs have been isolated; we have now begun to analyse the effects of expressing the c-ski proteins in the whole animal.
对具有重要农业价值的动物进行品系改良，将需要高效的基因导入技术、调控新导入基因表达的能力，而最重要的是，需要鉴定出那些合适表达能够改良动物性状的基因。我们已经开发出一系列禽逆转录病毒载体，可用于将新的遗传信息导入鸡的生殖系，因为对于鸡而言，无法通过将DNA直接显微注射到受精卵中来创建转基因动物。我们已经鉴定出鸡骨骼肌α-肌动蛋白基因的一个220 bp片段，该片段可使其他基因在横纹肌中特异性表达。这个鸡启动子在转基因小鼠中显示出正确的组织特异性，推测也可用于其他哺乳动物物种。骨骼肌α-肌动蛋白启动子已被插入禽逆转录病毒载体中，并且该启动子在被这些逆转录病毒载体感染的培养细胞中具有功能。逆转录病毒载体携带的骨骼肌α-肌动蛋白启动子表达的组织特异性将很快在体内进行测试。我们正在研究两类可能对品系改良有用的基因：能够产生对致病性病毒感染的显性抗性的基因，以及在肌肉发育中可能起关键作用的基因。逆转录病毒包膜糖蛋白的表达可特异性阻断病毒用于感染易感细胞的细胞受体。在转基因鸡中表达禽白血病病毒A亚群包膜可防止同一亚群的致病性病毒感染。我们正试图通过表达网状内皮组织增生症病毒包膜糖蛋白来阻断网状内皮组织增生症病毒感染。我们已经证明可以在培养细胞中阻断感染，并且我们现在正在创建用于体内实验的逆转录病毒载体。我们还开始研究ski癌基因的细胞同源物，该基因已被证明在体外可刺激鹌鹑成肌细胞的分化。已分离出具有生物活性的cDNA；我们现在已经开始分析在整个动物中表达c-ski蛋白的效果。
